1. Field of Invention
The invention relates to a sewing machine having a needle bar up/down moving mechanism, a needle bar oscillating mechanism, a needle bar interrupting mechanism that interrupts the needle bar up/down moving mechanism from moving the needle bar up and down, a thread tension adjusting mechanism, and a thread tension releasing mechanism and, in particular, to a sewing machine where the needle bar oscillating mechanism, the needle bar interrupting mechanism, and the thread tension releasing mechanism are driven by a common actuator.
2. Description of Related Art
Conventionally, a zigzag sewing machine capable of sewing straight and zigzag patterns, includes a plurality of sewing devices, such as a thread tension adjusting mechanism that adjusts a tension of a needle thread by sandwiching the needle thread between a pair of thread tension disks, a needle bar up/down moving mechanism that moves the needle bar up and down, and a needle bar oscillating mechanism that oscillates the needle bar in a direction perpendicular to a feeding direction of a work cloth. This kind of zigzag sewing machine optionally includes a needle bar interrupting mechanism, that interrupts the needle bar up/down moving mechanism from moving the needle bar up and down, and a tension releasing mechanism, that allows the thread tension mechanism to release the needle thread tension, which work in the case where the needle bar is temporarily stopped for making an extreme long stitch, such as basting, or the upper and lower threads are automatically cut by the thread trimming mechanism in the middle of or at the end of sewing.
In this case, the needle bar up/down moving mechanism is driven because a main shaft is rotated by a machine motor, and the needle bar is oscillated via the needle bar oscillating mechanism driven by an exclusive electric motor. The needle bar interrupting mechanism is independently driven by an electric actuator, such as a solenoid, which is exclusively provided. The tension releasing mechanism is also independently driven by an electric actuator, such as a solenoid, which is also exclusively provided. Namely, the needle bar oscillating mechanism, the needle bar interrupting mechanism, and the tension releasing mechanism are separately driven by an exclusive motor or electric actuator. The problems are the cost of manufacturing becomes higher and the assembly operation becomes complicated because electric motors and actuators are attached to a machine, which further result in a larger size of the sewing machine.
As a result, recently proposed sewing machines have fewer electric actuators because a plurality of mechanisms, such as the needle bar oscillating mechanism and the needle bar interrupting mechanism, are driven by one actuator.
For example, in the needle bar disengaging mechanism of a zigzag sewing machine disclosed in Japanese Utility Model Publication No. 2-36455, the needle bar is oscillated via an oscillating rod when a zigzag pulse motor is driven within a specified rotating angle. On the other hand, when the pulse motor is driven more than the specified rotating angle, a disengaging link is rotated, and a disengaging clutch plate is activated to release the coupling of the needle bar driving mechanism. Then, finally, the needle bar is disengaged.
In the machine disclosed in U.S. Pat. No. 4,619,214, the head includes a servomotor and a cam having two laterally presented faces B, C and ramp A1, A2, A3, which is driven by the servomotor. When the servomotor drives the cam, the two faces B, C make contact with a pair of feelers to oscillate the needle bar. Simultaneously, a feeler makes contact with ramp A1, A2, A3 to interrupt the needle bar from moving up and down.
In the needle bar disengaging mechanism of the zigzag sewing machine in Japanese Utility Model Publication No. 2-36455 and the sewing machine in U.S. Pat. No. 4,619,214, the needle bar oscillating mechanism and the needle bar interrupting mechanism are driven by the combination of an electric motor and a cam, in order to decrease the number of actuators. When the tension releasing mechanism, that allows the thread tension mechanism to release the needle thread so as to automatically pay it out for thread trimming, is provided, an electric actuator to drive the tension releasing mechanism is additionally required. Furthermore, a control element is required, such as a high specification CPU that has an additional output port for driving the electric actuator. Therefore, this makes the cost higher and the size of the machine larger.